Hi I am Zotero and Obsidian user. I use a
simple Zotero translator that creates a markdown link to your Zotero Item when quick copying (drag and dropping) the item into obsidian.
You could find the link here Zotero best practices - #72 by silent
Can you open the pdf from Zotero and the problem arise only when you are using Obsidain?
In my case I don’t link to pdf, but to Zotero bibliographic entry containing that item, for example
[van der Plas. 2020. Entraining neurons via noninvasive electric stimulation improves cognition](zotero://select/items/1_946JX82F)